Speed Control
 

Hello all.

I was looking at the router speed control from Woodcraft
(http://shop.woodcraft.com/Woodcraft/...C6E39C42114560
) and had a question. I know there has been somewhat of a
disagreement in the past as to whether these things will tear up your
router motor or not, but my question is more general. It is stated
that it will work on any "motor with replaceable brushes." Why? Why
not a brushless motor (i.e., a table saw)?

I realize this may be some simple electronics question or something,
but I'd appreciate any info you guys might have.

cmk8895

Speed Control
 

The speed of an AC synhronous motor as would be used on a belt driven table
saw is a function of the number of poles in the motor and the frequency of
the supplied AC power (which is 60 Hz in North America).

So, to vary the the speed of an AC synchronous motor you must use a variable
frequency controller which is not a cheap endeavour.

DC motors speeds are varied by altering the supplied voltage. DC motors are
brushed motors. I anticipate that is what is happening with the device you
mention.

Dave

"Matt" wrote in message
om...
Hello all.

I was looking at the router speed control from Woodcraft

(http://shop.woodcraft.com/Woodcraft/...%5Fid=3957&gif
t=False&mscssid=013CC5175C03A4EE58C6E39C42114560
) and had a question. I know there has been somewhat of a
disagreement in the past as to whether these things will tear up your
router motor or not, but my question is more general. It is stated
that it will work on any "motor with replaceable brushes." Why? Why
not a brushless motor (i.e., a table saw)?

I realize this may be some simple electronics question or something,
but I'd appreciate any info you guys might have.

cmk8895

Speed Control
 

I'll clarify further that a "universal motor" is a brushed motor that can be
either AC or DC powered. Universal motors are commonly used in small tools
and hosehold items. Universal motors are essentially the same as a DC motor
and are also speed controllable by varying voltage supply.

Dave

Speed Control
 

"Matt" wrote in message
om...
Hello all.

I was looking at the router speed control from Woodcraft

(http://shop.woodcraft.com/Woodcraft/...%5Fid=3957&gif
t=False&mscssid=013CC5175C03A4EE58C6E39C42114560
) and had a question. I know there has been somewhat of a
disagreement in the past as to whether these things will tear up your
router motor or not, but my question is more general. It is stated
that it will work on any "motor with replaceable brushes." Why? Why
not a brushless motor (i.e., a table saw)?

I realize this may be some simple electronics question or something,
but I'd appreciate any info you guys might have.

cmk8895

Single phase AC motors are considered fixed speed devices their speed is
determined by the number of poles in the motor. You will also hear them
refered to as induction motors, this is because the energy comes in the form
of induced magnetic fields, i.e. no direct electrical connection between the
stator and rotor.

Brush type motors on the other hand have their electrical supply applied
directly to the rotor and most commonly have permanent magnets, their speed
of rotation is dependent on the average voltage supplied to them. When
supplied from a device like a speed controller that voltage is being turned
on and off continuously, the ratio of the on to off time determines the
effective voltage being supplied to the motor and thus the motor speed.

Speed Control
 

Bernard Randall wrote:
"Matt" wrote in message
om...

Hello all.

I was looking at the router speed control from Woodcraft


(http://shop.woodcraft.com/Woodcraft/...%5Fid=3957&gif
t=False&mscssid=013CC5175C03A4EE58C6E39C42114560

) and had a question. I know there has been somewhat of a
disagreement in the past as to whether these things will tear up your
router motor or not, but my question is more general. It is stated
that it will work on any "motor with replaceable brushes." Why? Why
not a brushless motor (i.e., a table saw)?

I realize this may be some simple electronics question or something,
but I'd appreciate any info you guys might have.

cmk8895


Single phase AC motors are considered fixed speed devices their speed is
determined by the number of poles in the motor. You will also hear them
refered to as induction motors, this is because the energy comes in the form
of induced magnetic fields, i.e. no direct electrical connection between the
stator and rotor.

Brush type motors on the other hand have their electrical supply applied
directly to the rotor and most commonly have permanent magnets, their speed
of rotation is dependent on the average voltage supplied to them. When
supplied from a device like a speed controller that voltage is being turned
on and off continuously, the ratio of the on to off time determines the
effective voltage being supplied to the motor and thus the motor speed.


I understand speed controllers but not why you would want one on a router.
For a handheld router, any bit large enough to require reducing the
speed is probably too large to use safely hand held. In general most
people use larger routers in tables and they all seem to have variable
speed built in. So where does the use of a speed controller come in?
John

Speed Control
 

"John Siegel" wrote in message
...


I understand speed controllers but not why you would want one on a router.
For a handheld router, any bit large enough to require reducing the
speed is probably too large to use safely hand held. In general most
people use larger routers in tables and they all seem to have variable
speed built in. So where does the use of a speed controller come in?
John


Some of us cheapskates have a still-working, older, high-horsepower
router, and we'd like to slow it down when putting it in the table. If
old reliable ever breaks down, I guess I'll get one of them new-fangled
variable-speed jobbies.

Henry

Speed Control
 

John Siegel writes:
I understand speed controllers but not why you would want one on a
router. For a handheld router, any bit large enough to require
reducing the speed is probably too large to use safely hand held.

Speed controllers are also used when small bits need to be run slower,
such as with woods prone to burning or delicate or intricate cuts
where you can't move the router fast enough to avoid burning.
Especially with piloted bits instead of bearing bits.

At least, that's what I use my speed controller for.

Speed Control
 

"DJ Delorie" wrote in message
...

John Siegel writes:
I understand speed controllers but not why you would want one on a
router. For a handheld router, any bit large enough to require
reducing the speed is probably too large to use safely hand held.

Speed controllers are also used when small bits need to be run slower,
such as with woods prone to burning or delicate or intricate cuts
where you can't move the router fast enough to avoid burning.
Especially with piloted bits instead of bearing bits.

At least, that's what I use my speed controller for.

I second those thoughts, in addition:

If you ever make cabinet doors you end up with long grain and end grain at
the top and bottom of the doors, this is normally cut with some form of
decorative bit. The end grain needs to be cut at about 1/2 the speed of the
long grain else you end up with burn marks that are almost impossible to get
rid of.

Complexity of outline, bit and wood charactaristics need balancing with
spindle speed.

For a bench router you really need the meanest plain machine you can get, I
had a big old Makita at one stage, no soft start, no speed control, a bitch
to hand hold but great in a table with a separate speed controller.

Bernard R

Speed Control
 

Related to all the comments in this thread:

- My floor drill press is on its slowest speed.
- My variable speed router in the table (DW 621) is set about as slow as
it can go.

Woodworking is a hobby, a diversion. I don't mind going slower than a CNC.
g On the drill press, Forstner, spade and twist bits seem to do just
fine at 120 RPM (or whatever the slowest speed is.) On the router table, I
don't get burn marks very much anymore.

Production throughput issues aside, is there any reason to not run routers
and drills as slow as they can go?

-- Mark

Speed Control
 

Production throughput issues aside, is there any reason to not run
routers and drills as slow as they can go?

OT g

I suppose, as far as router bits go, it's related to the speed of the
cutting edge of the bit vs. the reaction speed of the material. If a
tornado can jam a straw into a tree trunk, the cutting edge of a router bit
going fast enough could cut off the waste before chipout could occur.
Thought experiment: A router bit turning at one revolution per month would
have a tendancy to split the wood, as the pressure along the grain would
build up gradually. A router bit edge at 10% of the speed of light would
probably slice off anything before the remaining material perceived at the
molecular level that it had been disconnected from the waste.

But AFAIK we don't have the materials that will hold together at 10% of the
speed of light. I know Grizzly doesn't carry a feeder that can put a piece
of pine past a router quick enough to avoid burning... g

/OT

-- Mark

Speed Control
 

Carbide is not really a very good cutting material. It produces far more
cutting pressure than steel. It depends, to a certain degree, on high speed
to cut freely. Running it to slow can be a problem. That said, I have routed
successfully at 3000 RPM though it would have gone much better at a higher
speed. As for drilling, to slow is better than to fast. Many of the speed
charts I have seen recommend speeds that are way to fast. Many poor quality
holes can be attributed to to high RPM.
"Mark Jerde" wrote in message
...
Production throughput issues aside, is there any reason to not run
routers
and drills as slow as they can go?

-- Mark

Speed Control
 

"Mark Jerde" wrote in message
...
Related to all the comments in this thread:

- My floor drill press is on its slowest speed.
- My variable speed router in the table (DW 621) is set about as slow
as
it can go.

Woodworking is a hobby, a diversion. I don't mind going slower than a
CNC.
g On the drill press, Forstner, spade and twist bits seem to do just
fine at 120 RPM (or whatever the slowest speed is.) On the router table,
I
don't get burn marks very much anymore.

Production throughput issues aside, is there any reason to not run routers
and drills as slow as they can go?

-- Mark


It depends on your ability to feed the tool into the material slowly and
smoothly enough, which will depend very much on the material and tool shape.
As an example, no matter how hard you pressed and how slow you rotated a
standard drill bit in a hand cranked drill into a piece of steel it would
still cut, if you did the same to a piece of wood the bit would dig in and
stall. For interupted cuts as an edge with a router bit it depends on the
tooth load, I don't know the figures for wood, but typical tooth load for
milling steel is in the order of 0.0002" for a 1/4" end mill rising to
0.003" for a 3".

Bernard R

Speed Control
 

"Bernard Randall" wrote in message
...
If you ever make cabinet doors you end up with long grain and end
grain at
the top and bottom of the doors, this is normally cut with some form
of
decorative bit. The end grain needs to be cut at about 1/2 the
speed of the
long grain else you end up with burn marks that are almost
impossible to get
rid of.

Bernard R

This is a new one to me. I've routed some rails and stiles and I've
always
ran the router at the same speed for both cuts. I occasionally have
had
a little burning at the end grain but usually adjusted my feed speed
to
compensate. I would think that if you slowed the bit down to 1/2
speed
there would be more of a tendency for tear-out somewhere along the
way.
I do back up the end grain cuts with a scrap block of wood so I
haven't
had the problem at the corner of the rail. I don't usually use large
diameter
bits so I'm not used to slowing my router down too much.

Bruce
Redding, Ca.

Speed Control
 

"Bruce" wrote in message
...

snip

This is a new one to me. I've routed some rails and stiles and I've
always
ran the router at the same speed for both cuts. I occasionally have
had
a little burning at the end grain but usually adjusted my feed speed
to
compensate. I would think that if you slowed the bit down to 1/2
speed
there would be more of a tendency for tear-out somewhere along the
way.
I do back up the end grain cuts with a scrap block of wood so I
haven't
had the problem at the corner of the rail. I don't usually use large
diameter
bits so I'm not used to slowing my router down too much.

Bruce
Redding, Ca.



My experience has been that routing end grain requires much more force than
with the grain, after all each fibre is being sheared at 90 deg, and this
puts a greater load on the operator and machine. By reducing the force and
hence feed rate also reducing motor speed keeps the chip load constant which
maintains quality of cut.


Bernard R